Credible number left in Lincoln? (7)
I believe the answer is:
tenable
'credible' is the definition.
(thesaurus)
'number left in lincoln?' is the wordplay.
'number' becomes 'ten' (ten is a kind of whole number).
'left' becomes 'l' (common abbreviation).
'in' indicates putting letters inside.
'lincoln?' becomes 'abe'.
'l' going within 'abe' is 'able'.
'ten'+'able'='TENABLE'
(Other definitions for tenable that I've seen before include "Able to be believed" , "Able to be held" , "Capable of being kept" , "possible to maintain" , "fairly arguable" .)